Fabric is a flexible material consisting of a network of natural or artificial fibers often referred to as thread or yarn. Yarn is produced by spinning raw fibers such as wool, linen, cotton, or other natural or manmade material on a spinning wheel to produce long strands. Fabrics are formed by weaving, knitting or by non-woven techniques.
The fabrics woven and terry woven are made from, for example, 100% cotton fiber yarns, fiber blends in yarns like: cotton and viscose, blends of cotton and modal, blends of silk and modal; bamboo fiber yarns; and blends of cotton and bamboo yarns.
Flat fabrics, such as sheeting or apparel, may be made from 100% cotton; blends of polyester and cotton; blends of polyester and viscose; blends of cotton and modal; blends of cotton, silk and modal; and any combinations thereof.
Further, most fibers have absorbent properties but the extent of absorption depends on the type of fiber, nature of yarn used and the design of the fabric etc.
However, by suitable modifications in the yarn structure, it is possible to increase the wicking property of the yarn, in effect increasing the hydrophilic nature, thereby making the yarns quick absorbing and bulky.
Terry Towels are generally thick materials. The thicker the towel, the greater the surface area, and thus a greater amount of water can be absorbed. When a towel fabric encounters a water droplet, the pile loops first remove the droplet by sucking the droplet between the space available among the pile loops and then absorbing the water inside the yarn in the space between the fibers in the yarn. The latter part applies to flat fabrics as well. The absorbed water then enters the secondary wall and in lumen of the cotton fiber.
The amount of twist in the yarn affects the properties of the towel products. The pile yarn is generally a low-twist yarn. Pile loops provide maximum surface area for the absorption of water, and the low twist aids in the absorption by imparting wicking properties to the yarn. Ground warp and weft are generally hard-twisted compared to the pile yarn. The ground and weft yarn twist factors generally range from about 3.8 to about 4.2, depending upon the towel construction. In contrast, the twist factor in the pile yarn generally ranges from about 3.2 to about 3.9. Similarly in the case of flat fabrics the twist factor for warp and weft range from about 3.8 to about 4.5.
The yarns normally used in terry fabrics are coarse and range from Ne (Number English) 8s to 30s in single as well as doubled configuration for pile, weft and ground yarns.
Similarly the warp and weft yarn count, in the case of flat fabrics range from Ne. 12s to Ne. 100s in single as well as doubled configuration depending on the construction of fiber, their blends and the structure of the yarn made thereof.
Decorative designs and embellishments are formed using polyester filament, polyester spun yarn, viscose filament yarn, viscose spun yarn, mercerized cotton yarn, cotton linen fiber blended yarns, Ramie cotton fiber blended yarn, modal fiber yarns, chenille yarn, modified viscose fiber yarn, and combinations thereof. Other flat fabrics such as sheeting or apparel are made from 100% cotton fiber yarn; fiber blends of polyester and cotton; blends of polyester and viscose; blends of cotton and modal, blends of cotton and silk and modal; blends of cotton and bamboo; blends of cotton and sea weed fibers; blends of cotton and sliver fibers; blends of cotton and charcoal fibers; and any combinations thereof.
The greater the amount of free air space available within the yarn, the quicker and higher absorption of the water. Hence, to increase the amount of free spaces, (as the air space increases, the drying of the towel after absorption also increases) structural changes in the yarn have to be made.
Polyvinyl alcohol (“PVA”), a man made fiber, has the unique property of dissolving in hot water. Earlier invention(s) exploits the dissolving property of PVA by introducing PVA into blended yarns and, for example, in core of the cotton yarn.
There are various methods of introducing PVA into cotton yarn via cotton spinning system. These methods have been exploited earlier. These methods are:
a) Inserting PVA fibers into the core during ring spinning, by inserting PVA spun yarn into the stream of cotton fibers in the drafting zone during ring spinning on Ring Frame.
b) Blending the PVA roving with the cotton roving during feeding in the drafting system of ring frame in SIRO spinning system.
c) Inserting PVA fiber slivers into the middle of cotton slivers at the feeding end of the drafting zone of the speed frame, twisting on the speed frame, and subsequently spinning the yarn at ring spinning.
d) Blending PVA fiber along with cotton fiber in the initial process of fiber mixing in cotton spinning system.
e) Doubling PVA yarn with cotton yarn with twist in reverse direction of cotton yarn leaving the final finished fabric with cotton yarn having only few turns of twist.
By using methods (a), (b) and (c) the blend homogeneity, across the radial direction in the final yarn structure, can not be ascertained. Also, by using these methods well interlinked ‘through pores’ through out the cross section of the yarn and on the surface of the yarn cannot be achieved. The pores formed are mainly of ‘closed’ and ‘blind’ type. The yarn made by these methods may be hollow in core but the surface is covered. Covered surface does not allow water to go inside the core in hollow space so easily. These methods are thus, not effective to attain the porous yarn structure in the final fabric. The structural difference in these yarn structure and invented can be well understood from schematic diagram in FIG. 1.
By using process (d) porous yarn structure in the final fabric can be attained. This process has operational challenges in blended process due to entirely different processing behavior of PVA fibers.
Process (e) involves separate spinning process for PVA yarn and Cotton Yarn. Therefore an additional cost of doubling process with PVA yarn is added making the process cost ineffective. Also structure of the yarn is open fiber structure which causes negligible binding of the fibers.
Thus, there is a need for an economic and cost effective process of manufacturing air rich fabric/yarns with pores throughout the cross section.